Spinal Cord Injury without Radiographic Abnormality and the Chiari Malformation: Controlled Observations

Abstract

Background: Case reports have suggested an association between the Chiari malformation type 1 (CM1) and spinal cord injury without radiographic abnormality (SCIWORA). No controlled observations have appeared. We report a case-control study. Methods: The Kids' Inpatient Database (KID) is a product of the Healthcare Utilization Project of the Agency for Healthcare Research and Quality. For the years 1997, 2000, 2003, 2006, and 2009, the KID includes discharge data abstracted from almost 14 million pediatric admissions. We hypothesized that CM1 predisposes children to SCIWORA in the cervicomedullary region, and we reasoned that, if this hypothesis were true, then KID admissions coded for upper cervical SCIWORA would be associated with CM1 more frequently than admissions coded for lower cervical SCIWORA. Results: After exclusion of admissions with a variety of confounding diagnostic codes, we identified 754 admissions coded for upper cervical SCIWORA and 424 coded for lower cervical SCIWORA. Concurrent coding for CM1 was more prevalent among admissions coded for upper cervical SCIWORA than for lower cervical SCIWORA, but the difference did not attain statistical significance (p = 0.093; Fisher's exact test). Conclusions: These controlled observations fail to support the hypothesis that CM1 is associated with SCIWORA in childhood. If there is a real association, in the context of recent estimates of the prevalence of CM1 in the pediatric population, the magnitude of the incremental risk must be very small.